Embodiments of the present invention generally relate to systems and methods for dispensing electrostatically atomized active materials without the use of volatile organic compounds (“VOCs”). More specifically, embodiments of the present invention generally relate to systems and methods for rapidly atomizing and dispersing insecticides and similar low electrical conductivity fluids without the use of propellants and other additives.
The aerosol can dispenser is a staple of modern society. Produced by the billions, the modern aerosol can is capable of dispensing, on demand, high flow-rate (gram/sec), finely aerosolized doses of a wide array of products. Despite its continued refinement and utility, the aerosol can dispenser is a fundamentally inefficient and polluting means for spray generation and transfer of active material to a target.
By way of example, a popular, archetypical insecticidal aerosol can has a net weight of about 370 grams (13 ounces) of which the active ingredients (Pyrethrins) and “related” materials (including “petroleum distillate”) account for less than 2% of the total weight of ingredients. The remaining “inert” material, some 98.087%, is required for the aerosolization process. To atomize and disperse less than eight grams of active material requires in excess of 360 grams of environmentally detrimental propellant/diluent plus a costly pressure vessel and atomizing nozzle.
The aerosol can dispenser is simply a hydraulic or gas assisted nozzle. Operational pressure (of about 5 bar), consisting of hydraulic pressure, propellant vapor, or a combination of the two, mechanically and aerodynamically converts bulk fluid into a directed droplet plume. With a broad droplet size distribution characterized by a significant population of small (<10 micron) droplets, these readily stagnated aerosols also present a respirable health hazard. This highly inefficient atomization and dispersal process is effective, but it is so at a cost. The environmental impact of the propellants dumped into the atmosphere, discarded pressure vessels, and the inhalation health hazards of repeated exposure to the spray are costs that have yet to be to be fully addressed.
Well-proven direct charge injection electrostatic atomizer technology provides high instantaneous flow rates of the small volumes of active ingredients required for all applications of interest. Charged spray droplets so produced are self-dispersive, preferentially enveloping and wrapping around the target. Transfer of fluid to the target is inherently more effective than is possible using conventional aerosol dispensers. Of equal importance, the charged spray cannot form a respirable cloud. Having droplet size distributions three or more times narrower than non-charged sprays, small (<10 microns) and large (≧100 microns) droplets are absent. All droplets are charged, attracted to the target, and cannot be inhaled.
Most importantly, modest feed pressures (less than one bar) available by hand pumping are sufficient to generate self-dispersive small droplet plumes. This capability permits the elimination of VOCs such as propellants and diluents as well as the high-pressure container previously required for atomization/dispersion. However, current manifestations of direct charge injection electrostatic atomizers are bulky and costly.
What is needed is an alternative aerosolization and/or dispensing apparatus that eliminates the propellants and/or diluents inherent in aerosol can operation. It is an object of this invention to provide a disposable, hand-held, low-pressure electrostatic atomizer capable of providing the same level of low-cost, operator-friendly convenience of an aerosol can without detrimental impact on the environment or user health and in which only “active”, undiluted ingredients are sprayed.